Rotating electric machine and vehicle equipped with rotating electric machine

ABSTRACT

A rotating electric machine includes a stator core, a stator winding, and a rotor rotatably disposed via an air gap so as to be allowed to rotate relative to the stator core. A magnetic resistance-altering portion is provided on every other magnetic pole of magnetically-assisted salient pole members. A magnetic pole provided with the magnetic resistance-altering portion and a magnetic pole without the magnetic resistance-altering portion are alternately arranged.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/830,476, filed Dec. 4, 2017, which is a continuation of U.S.application Ser. No. 14/372,632, filed Jul. 16, 2014, which is aNational Stage application of International Application No.PCT/JP2013/050183, filed Jan. 9, 2013, and which claims priority toJP-2012-008565, filed Jan. 19, 2012, the entire disclosures of which areherein expressly incorporated by reference.

TECHNICAL FIELD

The present invention relates to a rotating electric machine and avehicle equipped with the rotating electric machine.

BACKGROUND ART

The winding technologies adopted in conjunction with rotating electricmachines used to drive vehicles include that disclosed in patentliterature 1. In addition, the technologies pertaining to rotors knownin the related art include the art disclosed in patent literature 2.

CITATION LIST Patent Literature

Patent literature 1: U.S. Pat. No. 6,894,417

Patent literature 2: Japanese Laid Open Patent Publication No.2010-98830

SUMMARY OF INVENTION Technical Problem

A rotating electric machine mounted in an electric vehicle or the likeis required to operate without generating any significant noise.Accordingly, an object of the present invention is to achieve noisereduction in a rotating electric machine.

Solution to Problem

According to one aspect of the present invention, a rotating electricmachine, comprises: a stator core having a plurality of slots formedtherein; a stator winding assuming a plurality of phases, which includesa plurality of coil windings wound with a wave winding pattern, eachmade up with slot conductors each inserted at one of the slots at thestator core to form one of a plurality of layers and cross conductorseach connecting same-side ends of slot conductors inserted at differentslots so as to form a coil end; and a rotor rotatably disposed via anair gap so as to be allowed to rotate relative to the stator core, whichincludes a plurality of magnets and a plurality of magnetic auxiliarysalient pole portions each formed between poles formed with the magnets,wherein: the cross conductors connect the slot conductors so as to runastride slots with a slot pitch Np set to N+1 at coil ends on one sideand run astride slots with the slot pitch Np set to N−1 at coil ends onanother side, with N representing a number of slots per pole; the statorwinding includes a plurality of slot conductor groups each made up witha plurality of slot conductors corresponding to a single phase; theplurality of slot conductors in each slot conductor group are insertedat a predetermined number Ns of successive slots forming a continuousrange along a circumference of the stator core so that the slotconductors in the slot conductor group take successive slot positionsand successive layer positions; and the predetermined number Ns is setso that Ns=NSPP+NL when NSPP represents a number of slots per pole perphase and a number of layers is expressed as 2×NL; the rotor includesmagnetic resistance-altering portions located at positions each offsetalong a circumferential direction from a q-axis passing through a centerof a salient pole at a corresponding magnetic auxiliary salient poleportion within the magnetic auxiliary salient portion; and extents towhich the magnetic resistance-altering portions are offset from theq-axis vary depending upon positions assumed by the magnetic auxiliarysalient poles so that torque pulsations occurring in a applying currentstate cancel each other out.

According to another aspect of the present invention, a vehicle,comprises: a rotating electric machine according to any one of the firstthrough tenth aspects; a battery that provides DC power; and aconversion device that converts the DC power originating from thebattery to AC power and provides the AC power to the rotating electricmachine, wherein: torque generated in the rotating electric machine isused as a drive force to drive the vehicle.

Advantageous Effect of the Invention

According to the present invention, noise reduction can be achieved in arotating electric machine and a vehicle equipped with the rotatingelectric machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A schematic diagram showing the structure of a hybrid electricvehicle

FIG. 2 A circuit diagram pertaining to the power conversion device 600

FIG. 3 A sectional view of the rotating electric machine 200

FIG. 4 Illustrations of the rotor core 252

FIG. 5 Sectional views of the stator 230 and the rotor 250

FIG. 6 A perspective view of the stator 230

FIG. 7 A connection diagram pertaining to the stator winding 238

FIG. 8 A detailed connection diagram pertaining to the U-phase winding

FIG. 9 A part of the U1-phase winding group in an enlargement

FIG. 10 A part of the U2-phase winding group in an enlargement

FIG. 11 A diagram indicating the positional arrangement with which theslot conductors 233 a are disposed

FIG. 12 Diagrams indicating the positional arrangement among the slotconductors 233 a

FIG. 13 Partial sectional views of the stator 230 and the rotor 250 inenlargements

FIG. 14 An illustration of reluctance torque

FIG. 15 Illustrations indicating a magnetic flux distribution that maymanifest in non-applying current state

FIG. 16 A diagram illustrating how the cogging torque may be reduced

FIG. 17 A graph indicating the relationship between the ratio τm/τprepresenting the degree of arc at the magnet poles and the coggingtorque

FIG. 18 A diagram indicating waveforms of the cogging torque

FIG. 19 A diagram indicating waveforms of the induced voltage

FIG. 20 A diagram providing results obtained by analyzing the higherharmonic component in the induced voltage waveforms

FIG. 21 A diagram indicating waveforms of the torque induced bysupplying an AC current

FIG. 22 A diagram providing results obtained by analyzing the higherharmonic component in the torque waveforms

FIG. 23 An illustration of the toroidal 0th-order vibration mode at thestator

FIG. 24 An illustration of the toroidal 6th-order vibration mode at thestator

FIG. 25 An illustration of the vibration mode taking on the toroidal6th-order component at the stator, in which the phase is reverse at thetwo ends facing opposite each other along the axial direction

FIG. 26 A detailed connection diagram pertaining to the U-phase windingachieved in a second embodiment

FIG. 27 A diagram indicating the positional arrangement with which theslot conductors 233 a are disposed in the second embodiment

FIG. 28 A detailed connection diagram pertaining to a part of theU-phase winding achieved in a third embodiment

FIG. 29 A diagram indicating the positional arrangement with which theslot conductors 233 a are disposed in the third embodiment

DESCRIPTION OF EMBODIMENTS

The following is a description of embodiments of the present invention,given in reference to the drawings.

First Embodiment

The rotating electric machine according to the present inventionachieves noise reduction by reducing the extent of torque ripple. Forthis reason, it is ideal in applications in which it is used as atraveling motor for an electric vehicle. While the rotating electricmachine according to the present invention may be adopted in a pureelectric vehicle engaged in traveling operation exclusively on arotating electric machine or in a hybrid type electric vehicle drivenboth by an engine and a rotating electric machine, the followingdescription will be given by assuming that the present invention isadopted in a hybrid type electric vehicle.

FIG. 1 is a schematic illustration showing the structure of a hybridtype electric vehicle having installed therein rotating electricmachines achieved in an embodiment. An engine 120, a first rotatingelectric machine 200, a second rotating electric machine 202 and abattery 180 are mounted at a vehicle 100. When a drive force imparted bythe rotating electric machines 200 and 202 is required, the battery 180provides DC power to a power conversion device 600, which converts theDC power to AC power and supplies the AC power to the rotating electricmachines 200 and 202. In addition, during a regenerative travelingoperation, AC power generated at the rotating electric machines 200 and202 is supplied to the power conversion device 600, which converts theAC power to DC power and supplies the DC power to the battery 180. TheDC power from and into the battery 180 with the rotating electricmachines 200 and 202 are performed by exchanging via the powerconversion device 600. In addition, although not shown, a battery thatprovides low-voltage power (e.g., 14 V power) is installed in thevehicle so as to supply DC power to the control circuits to be describedbelow.

Rotational torque generated via the engine 120 and the rotating electricmachines 200 and 202 is transmitted to front wheels 110 via atransmission 130 and a differential gear unit 160. The transmission 130is controlled by a transmission control device 134, whereas the engine120 is controlled by an engine control device 124. The battery 180 iscontrolled by a battery control device 184. The transmission controldevice 134, the engine control device 124, the battery control device184, the power conversion device 600 and an integrated control device170 are connected with one another via a communication line 174.

The integrated control device 170, which is a higher order controldevice relative to the transmission control device 134, the enginecontrol device 124, the power conversion device 600 and the batterycontrol device 184, receives, via the communication line 174,information originating from the transmission control device 134, theengine control device 124, the power conversion device 600 and thebattery control device 184, indicating the statuses at the individuallower-order control devices. Based upon the information thus received,the integrated control device 170 generates, through arithmeticoperation, a control command for each corresponding control device. Thecontrol command generated through the arithmetic operation is thentransmitted to the particular control device via the communication line174.

The high-voltage battery 180, constituted with secondary battery cellssuch as lithium ion battery cells or nickel hydride battery cells, iscapable of outputting high-voltage DC power in a range of 250 to 600 Vor higher. The battery control device 184 outputs, via the communicationline 174, information indicating the state of charge/discharge in thebattery 180 and the states of the individual battery cell unitsconstituting the battery 180 to the integrated control device 170.

Upon judging, based upon the information provided by the battery controldevice 184, that the battery 180 needs to be charged, the integratedcontrol device 170 issues a power generation operation instruction forthe power conversion device 600. The primary functions of the integratedcontrol device 170 further include management of torque output from theengine 120 and the rotating electric machines 200 and 202, arithmeticprocessing executed to calculate the overall torque representing the sumof the torque output from the engine 120 and the torques output from therotating electric machines 200 and 202, and to calculate a torquedistribution ratio, and transmission of control commands generated basedupon the arithmetic processing results to the transmission controldevice 134, the engine control device 124 and the power conversiondevice 600. Based upon a torque command issued by the integrated controldevice 170, the power conversion device 600 controls the rotatingelectric machines 200 and 202 so as to output torque or generate poweras indicated in the command.

The power conversion device 600 includes power semiconductors thatconstitute inverters via which the rotating electric machines 200 and202 are engaged in operation. The power conversion device 600 controlsswitching operation of the power semiconductors based upon a commandissued by the integrated control device 170. As the power semiconductorsare engaged in the switching operation as described above, the rotatingelectric machines 200 and 202 are each driven to operate as an electricmotor or as a power generator.

When engaging the rotating electric machines 200 and 202 in operation aselectric motors, DC power provided from the high-voltage battery 180 issupplied to DC terminals of the inverters in the power conversion device600. The power conversion device 600 controls the switching operation ofthe power semiconductors so as to convert the DC power supplied to theinverters to three-phase AC power and provides the three-phase AC powerto the rotating electric machines 200 and 202. When engaging therotating electric machines 200 and 202 in operation as generators, therotors of the rotating electric machines 200 and 202 are rotationallydriven with a rotational torque applied thereto from the outside andthus, three-phase AC power is generated at the stator windings of therotating electric machines 200 and 202. The three-phase AC power thusgenerated is converted to DC power in the power conversion device 600and the high-voltage battery 180 is charged with the DC power suppliedthereto.

FIG. 2 is a circuit diagram pertaining to the power conversion device600 shown in FIG. 1. The power conversion device 600 includes a firstinverter device for the rotating electric machine 200 and a secondinverter device for the rotating electric machine 202. The firstinverter device comprises a power module 610, a first drive circuit 652that controls switching operation of power semiconductors 21 in thepower module 610 and a current sensor 660 that detects an electriccurrent at the rotating electric machine 200. The drive circuit 652 isdisposed at a drive circuit substrate 650.

The second inverter device comprises a power module 620, a second drivecircuit 656 that controls switching operation of power semiconductors 21in the power module 620 and a current sensor 662 that detects anelectric current at the rotating electric machine 202. The drive circuit656 is disposed at a drive circuit substrate 654. A control circuit 648disposed at a control circuit substrate 646, a capacitor module 630 anda transmission/reception circuit 644 mounted at a connector substrate642 are all shared by the first inverter device and the second inverterdevice.

The power modules 610 and 620 are engaged in operation with drivesignals output from the corresponding drive circuits 652 and 656. Thepower modules 610 and 620 each convert the DC power provided from thebattery 180 to three-phase AC power and provide the three-phase AC powerresulting from the conversion to a stator winding constituting anarmature winding of the corresponding rotating electric machine 200 or202. In addition, the power modules 610 and 620 convert AC power inducedat the stator windings of the rotating electric machines 200 and 202 toDC power and provide the DC power resulting from the conversion to thebattery 180.

As indicated in FIG. 2, the power modules 610 and 620 each include athree-phase bridge circuit constituted with serial circuits, eachcorresponding to one of the three phases, electrically connected inparallel between the positive side and the negative side of the battery180. Each serial circuit includes a power semiconductor 21 constitutingan upper arm and a power semiconductor 21 constituting a lower arm, andthese power semiconductors 21 are connected in series. Since the powermodule 610 and the power module 620 adopt circuit structuressubstantially identical to each other as shown in FIG. 2, the followingdescription focuses on the power module 610 chosen as a representativeexample.

The switching power semiconductor elements used in the embodiment areIGBTs (insulated gate bipolar transistors) 21. An IGBT 21 includes threeelectrodes: a collector electrode, an emitter electrode and a gateelectrode. A diode 38 is electrically connected between the collectorelectrode and the emitter electrode of the IGBT 21. The diode 38includes two electrodes; a cathode electrode and an anode electrode,with the cathode electrode electrically connected to the collectorelectrode of the IGBT 21 and the anode electrode electrically connectedto the emitter electrode of the IGBT 21 so as to define the directionrunning from the emitter electrode toward the collector electrode at theIGBT 21 as a forward direction.

It is to be noted that MOSFETs (metal oxide semiconductor field effecttransistors) may be used as the switching power semiconductor elements,instead. A MOSFET includes three electrodes: a drain electrode, a sourceelectrode and a gate electrode. The MOSFET does not require a diode 38,such as those shown in FIG. 2, since it includes a parasitic diode withwhich the direction running from the drain electrode toward the sourceelectrode is defined as the forward direction, present between thesource electrode and the drain electrode.

The upper and lower arms in the serial circuit corresponding to a givenphase are configured by electrically connecting the emitter electrode ofone IGBT 21 and the collector electrode of another IGBT 21 in series. Itis to be noted that while the figure shows the upper arm and the lowerarm corresponding to a given phase each constituted with a single IGBT,a large current control capacity needs to be assured in the embodimentand thus, a plurality of IGBTs are connected in parallel to constitutean upper arm or a lower arm in the actual power module. However, forpurposes of simplification, the following explanation is given byassuming that each arm is constituted with a single power semiconductor.

In the embodiment described in reference to FIG. 2, each upper arm orlower arm, corresponding to one of the three phases, is actuallyconfigured with three IGBTs. The collector electrode of an IGBT 21constituting the upper arm in a given phase is electrically connected tothe positive side of the battery 180, whereas the source electrode of anIGBT 21 constituting the lower arm in a given phase is electricallyconnected to the negative side of the battery 180. A middle pointbetween the arms corresponding to each phase (an area where the emitterelectrode of the upper arm-side IGBT and the collector electrode of thelower arm-side IGBT are connected) is electrically connected to thearmature winding (stator winding) at the corresponding phase at thecorresponding rotating electric machine 200 or 202.

The drive circuits 652 and 656, constituting drive units via which thecorresponding inverter devices are controlled, each generate a drivesignal used to drive the IGBTs 21 based upon a control signal outputfrom the control circuit 648. The drive signals generated at theindividual drive circuits 652 and 656 are respectively output to thegates of the various power semiconductor elements in the correspondingpower modules 610 and 620. The drive circuits 652 and 656 are eachconfigured as a block constituted with six integrated circuits thatgenerate drive signals to be provided to the gates of the upper andlower arms corresponding to the various phases.

The control circuit 648, which controls the inverter devices, isconstituted with a microcomputer that generates, through arithmeticoperation, a control signal (a control value) based upon which theplurality of switching power semiconductor elements are engaged inoperation (turned on/off). A torque command signal (a torque commandvalue) provided from a higher-order control device, sensor outputs fromthe current sensors 660 and 662, and sensor outputs from rotationsensors mounted at the rotating electric machines 200 and 202 are inputto the control circuit 648. Based upon these signals input thereto, thecontrol circuit 648 calculates control values and outputs controlsignals to the drive circuits 652 and 656 to be used to control theswitching timing.

The transmission/reception circuit 644 mounted at the connectorsubstrate 642, which electrically connects the power conversion device600 with an external control device, is engaged in information exchangewith another device via the communication line 174 shown in FIG. 1. Thecapacitor module 630, constituting a smoothing circuit via which theextent of DC voltage fluctuation occurring as the IGBTs 21 are engagedin switching operation is reduced, is electrically connected in parallelwith DC-side terminals of the first power module 610 and the secondpower module 620.

FIG. 3 shows the rotating electric machine 200 in FIG. 1 in a sectionalview. It is to be noted that since the structure of the rotatingelectric machine 200 is substantially identical to that of the rotatingelectric machine 202, the following description focuses on the structureadopted in the rotating electric machine 200, taken as a representativeexample. However, the structural features described below do not need tobe adopted in both rotating electric machines 200 and 202, as long asthey are adopted in either one of them.

A stator 230, held inside a housing 212, includes a stator core 232 anda stator winding 238. On the inner circumferential side of the statorcore 232, a rotor 250 is rotatably held over an air gap 222. The rotor250 includes a rotor core 252 fixed onto a shaft 218, permanent magnets254 and nonmagnetic contact plates 226. The housing 212 includes a pairof end brackets 214 at each of which a bearing 216 is disposed. Theshaft 218 is rotatably held via the bearings 216.

A resolver 224, which detects the positions of poles at the rotor 250and the rotating speed of the rotor 250, is disposed at the shaft 218.An output from the resolver 224 is taken into the control circuit 648shown in FIG. 2. The control circuit 248 outputs a control signal,generated based upon the output having been taken in, to the drivecircuit 652. The drive circuit 652, in turn, outputs a drive signal,generated based upon the control signal, to the power module 610. At thepower module 610, a switching operation is executed based upon thecontrol signal so as to convert DC power, provided from the battery 180,to three-phase AC power. This three-phase AC power is provided to thestator winding 238 shown in FIG. 3 and, as a result, a rotating magneticfield is generated at the stator 230. The frequency of the three-phaseAC current is controlled based upon an output value provided by theresolver 224 and the phases of the three-phase AC current relative tothe rotor 250 are also controlled based upon the output value providedby the resolver 224.

FIG. 4(a) shows the rotor core 252 of the rotor 250 in a perspective.The rotor core 252 is a three-stage structure constituted with twodifferent types of cores 301 and 302, such as those shown in FIG. 4(b).The length H2 of the core 302, measured along the axial direction, isset substantially equal to the sum of the lengths H1 of the cores 301along the axial direction.

FIG. 5 shows sections of the stator 230 and the rotor 250, with FIG.5(a) showing them in a sectional view taken along A-A passing throughthe core 301 (see FIG. 3) and FIG. 5(b) showing them in a sectional viewtaken along B-B passing through the core 302 (see FIG. 3). It is to benoted that FIG. 5 does not include an illustration of the housing 212,the shaft 218 and the stator winding 238. Numerous slots 237 and teeth236 are formed in a uniform pattern along the entire inner circumferenceof the stator core 232. Reference numerals are appended to only onerepresentative slot and an adjacent tooth in FIG. 5. Inside the slots237, a slot insulator (not shown) is disposed and a plurality of phasewindings corresponding to a U-phase, a V-phase and a W-phase,constituting the stator winding 238 in FIG. 3, are installed in theslots 237. Seventy two slots 237 are formed over equal intervals in theembodiment.

In addition, twelve holes 253, at which rectangular magnets are to beinserted, are formed near the outer circumference of the rotor core 252,over equal intervals along the circumferential direction. At each hole253, with the depth thereof ranging along the axial direction, apermanent magnet 254 is embedded and fixed with an adhesive or the like.The holes 253 are formed so as to achieve a greater width, measuredalong the circumferential direction, compared to the width of thepermanent magnets 254 (254 a and 254 b) measured along thecircumferential direction and thus, hole spaces 257, present on the twosides of each permanent magnet 254, function as magnetic gaps. Thesehole spaces 257 may be filled with an adhesive or they may be sealedtogether with the permanent magnets 254 by using a forming resin. Thepermanent magnets 254 function as field poles of the rotor 250 and therotor in this embodiment assumes a 12-pole structure.

The permanent magnets 254 are magnetized along the radial direction andthe magnetizing direction is reversed from one field pole to the next.Namely, assuming that the surface of a permanent magnet 254 a facingtoward the stator and the surface of the permanent magnet 254 a locatedon the axial side respectively achieve N polarity and S polarity, thestator-side surface and the axial-side surface of a permanent magnet 254b disposed next to the permanent magnet 254 a respectively achieve Spolarity and N polarity. Such permanent magnets 254 a and 254 b aredisposed in an alternate pattern along the circumferential direction.

The permanent magnets 254 may be magnetized first and then embedded inthe holes 253, or they may be inserted in the holes 253 at the rotorcore 252 in an unmagnetized state and then magnetized by applying anintense magnetic field to the inserted permanent magnets. Oncemagnetized, the permanent magnets 254 exert a strong magnetic force.This means that if the permanent magnets 254 are magnetized before theyare fixed at the rotor 250, the strong attracting force occurringbetween the permanent magnets 254 and the rotor core 252 is likely topresent a hindrance during the permanent magnet installation process.Furthermore, the strong attracting force imparted by the permanentmagnets 254 may cause foreign matter such as iron dust to settle on thepermanent magnets 254. For these reasons, it is more desirable, from theviewpoint of maximizing productivity in manufacturing the rotatingelectric machine, to magnetize the permanent magnets 254 after they areinserted at the rotor core 252.

The permanent magnets 254 may be neodymium-based sintered magnets,samarium-based sintered magnets, ferrite magnets or neodymium-basedbonded magnets. The residual magnetic flux density of the permanentmagnets 254 is approximately 0.4 to 1.3 T.

As the rotating magnetic field is induced at the stator 230 by thethree-phase AC currents (the three-phase AC currents flowing through thestator winding 238), torque is generated with the rotating magneticfield acting on the permanent magnets 254 a and 254 b at the rotor 250.This torque can be expressed as the product of the component in themagnetic flux imparted from the permanent magnets 254, which interlinkswith a given phase winding, and the component in the AC current flowingthrough the phase windings, which is perpendicular to the interlinkingmagnetic flux. Since the AC currents are controlled so as to achieve asine waveform, the product of the fundamental wave component in theinterlinking magnetic flux and the fundamental wave component in thecorresponding AC current represents the time-averaged torque componentand the product of the higher harmonic component in the interlinkingmagnetic flux and the fundamental wave component in the AC currentrepresents the torque ripple, i.e., the higher harmonic component of thetorque. This means that the torque ripple can be decreased by reducingthe higher harmonic component in the interlinking magnetic flux. Inother words, since the product of the interlinking magnetic flux and theangular acceleration with which the rotor rotates represents the inducedvoltage, reducing the higher harmonic component in the interlinkingmagnetic flux is equivalent to reducing the higher harmonic component inthe induced voltage.

FIG. 6 shows the stator 230 in a perspective. The stator winding 238 inthe embodiment is wound around the stator core 232 by adopting a wavewinding pattern. Coil ends 241 of the stator winding 238 are formed atthe two end surfaces of the stator core 232. In addition, lead wires 242of the stator winding 238 are led out on the side where one of the endsurfaces of the stator core 232 is located. Three lead wires 242 are ledout in correspondence to the U-phase, the V-phase and the W-phase.

In the connection diagram in FIG. 7 pertaining to the stator winding238, the connection method and the electrical phase relation among thephases of the individual phase windings are indicated. The statorwinding 238 in the embodiment is achieved by adopting a double starconnection, in which a first star connection, made up with a U1-phasewinding group, a V1-phase winding group and a W1-phase winding group, isconnected in parallel with a second star connection made up with aU2-phase winding group, a V2-phase winding group and a W2-phase windinggroup. The U1-phase winding group, the V1-phase winding group, theW1-phase winding group, the U2-phase winding group, the V2-phase windinggroup and the W2-phase winding group are each constituted with four coilwindings. Namely, the U1-phase winding group includes coil windings U11through U14, the V1-phase winding group includes coil windings V11through V14, the W1-phase winding group includes coil windings W11through W14, the U2-phase winding group includes coil windings U21through U24, the V2-phase winding group includes coil windings V21through V24 and the W2-phase winding group includes coil windings W21through W24.

As shown in FIG. 7, structures substantially identical to that adoptedin correspondence to the U phase are assumed for the V phase and the Wphase, and the individual phase winding groups in each star connectionare disposed so that the phase of the voltage induced at one phasewinding group is offset by 120° in electrical angle relative to thephase of the voltage induced at the next phase winding group along agiven direction. In addition, the angles formed by the coil windings inthe individual phase winding groups represent relative phases. While thestator winding 238 in the embodiment is achieved by adopting the doublestar (2Y) connection with two star connections connected in parallel, asindicated in FIG. 7, the stator winding 238 may instead adopt a singlestar (1Y) connection with two star connections connected in series,depending upon the level of voltage required to drive the rotatingelectric machine.

FIG. 8 provides a detailed connection diagram pertaining to the U-phasewinding groups constituting part of the stator winding 238, with FIG.8(a) showing the coil windings U13 and U14 in the U1-phase windinggroup, FIG. 8(b) showing the coil windings U11 and U12 in the U1-phasewinding group, FIG. 8(c) showing the coil windings U21 and U22 in theU2-phase winding group and FIG. 8(d) showing the coil windings U23 andU24 in the U2-phase winding group. As explained earlier, seventy-twoslots 237 are formed at the stator core 232 (see FIG. 5) and referencenumerals 01, 02, ˜71, 72 in FIG. 8 are slot numbers each assigned to aspecific slot.

The coil windings U11 through U24 are each made up with slot conductors233 a inserted through slots and cross conductors 233 b each connectingthe ends of slot conductors 233 a inserted through different slots,which are located on a specific side, so as to form a coil end 241 (seeFIG. 6). For instance, the end of a slot conductor 233 a insertedthrough the slot 237 assigned with slot No. 55 in FIG. 8(a), located onthe upper side in the figure, is connected to the upper-side end of aslot conductor 233 a inserted through the slot 237 assigned with slotNo. 60 via a cross conductor 233 b that forms an upper coil end, whereasthe lower end of the slot conductor 233 a inserted through the slot 237assigned with slot No. 55 is connected to the lower end of the slotconductor 233 a inserted through the slot 237 assigned with slot No. 48via a cross conductor 233 b that forms a lower coil end. A coil windingwith a wave winding pattern is formed by connecting the slot conductors233 a via the cross conductors 233 b as described above.

As will be explained in further detail later, four slot conductors 233 aare inserted side-by-side, from the inner circumferential side throughthe outer circumferential side, within each slot in the embodiment.These four slot conductors will be referred to as a layer 1, a layer 2,a layer 3 and a layer 4, starting on the innermost side and movingtoward the outer side. In FIG. 8, slot conductors in the coil windingsU13, U14, U21 and U22, each forming the layer 1, are indicated by solidlines and slot conductors in the coil windings U13, U14, U21 and U22,each forming the layer 2, are indicated by the one-point chain lines.Slot conductors in the coil windings U11, U12, U23 and U24, each formingthe layer 3, are indicated by solid lines and slot conductors in thecoil windings U11, U12, U23 and U24, each forming the layer 4, areindicated by the one-point chain lines.

It is to be noted that the coil windings U11 through U24 may each beformed by using a continuous single-piece conductor or they may each beformed by first inserting segment coils through the slots and thenconnecting the segment coils through welding or the like. The use of thesegment coils is advantageous in that coil ends 241 located at the twoends facing opposite each other along the axial direction, furtherbeyond the ends of the stator core 232, can be formed in advance beforeinserting the segment coils through the slots 237, which makes itpossible to easily create an optimal insulation distance betweendifferent phases or within a given phase. Such an optimal insulationdistance is bound to assure effective insulation through deterrence ofpartial discharge attributable to a surge voltage caused as the IGBTs 21are engaged in switching operation.

In addition, while the conducting material used to form the coilwindings may be a flat wire or a round wire or may be a conductingmaterial made up with numerous thin wires bundled together, the coilwinding is ideally formed by using a flat wire so as to maximize thespace factor to ultimately achieve a compact rotating electric machineassuring higher output and achieve higher efficiency.

FIGS. 9 and 10 respectively provide enlarged views of parts of theU1-phase winding group and the U2-phase winding group shown in FIG. 8.FIGS. 9 and 10 each provide a view of a part of the U1-phase windinggroup or the U2-phase winding group accounting for approximately fourpoles, which includes the area where a jumper wire is present. As shownin FIG. 9(b), the stator winding group U1, starting at the lead wire,enters the slot assigned with slot No. 71 as a layer-4 slot conductor,and then extends as a cross conductor 233 b astride a range equivalentto five slots before entering the slot assigned with slot No. 66 as alayer-3 slot conductor 233 a. Then, it leaves the layer-3 position inthe slot assigned with slot No. 66, runs astride a range equivalent toseven slots and leads into the slot assigned with slot No. 59 as alayer-4 slot conductor.

In other words, the stator winding is wound by assuming a wave windingpattern until it encircles the stator core 232 by a full turn as ittakes the layer-3 position in the slot assigned with slot No. 06 withits cross conductors 233 b located on the coil end side (the lower sidein the figure) where the lead wire is led out, each running astrideslots with the slot pitch Np set to 7 and its cross conductors 233 b,located on the opposite coil end side each running astride slots withthe slot pitch Np set to 5. This portion of the stator winding encirclesthe stator core by substantially a full turn and forms the coil windingU11 shown in FIG. 7.

Next, the stator winding, having left the layer-3 position in the slotassigned with slot No. 06, runs astride a range equivalent to six slotsand then leads into the slot assigned with slot No. 72 as a layer-4 slotconductor. The portion of the stator winding at the layer-4 position inthe slot assigned with slot No. 72 and beyond constitutes the coilwinding U12 shown in FIG. 7. As is the coil winding U11, the coilwinding U12 is formed by wave-winding the stator winding so as toencircle the stator core 232 by a full turn until it takes the layer-3position in the slot assigned with slot No. 06, with the crossconductors 233 b located on the side where the lead wire is present,each running astride slots with the slot pitch Np set to 7 and the crossconductors 233 b located on the opposite side each running astride slotswith the slot pitch Np set to 5. This portion of the stator windingencircles the stator core by substantially a full turn and forms thecoil winding U12.

It is to be noted that since the coil winding U12 is wound around thestator core with an offset relative to the coil winding U11, which isequivalent to a one-slot pitch, a phase difference in electrical angleequivalent to the one-slot pitch, manifests. The one-slot pitch isequivalent to 30° in electrical angle in the embodiment, andaccordingly, FIG. 7 clearly shows that the coil winding U11 and the coilwinding U12 are offset relative to each other by 30°.

The stator winding, having left the layer-3 position in the slotassigned with slot No. 07, leads into the slot assigned with slot No. 72as a layer-2 slot conductor (see FIG. 9(a)) via the jumper wire runningastride a range equivalent to seven slots. Subsequently, the statorwinding is wound around the stator core 232 so as to encircle the statorcore 232 by a full turn, from the layer-2 position in the slot assignedwith slot No. 72 through the layer-1 position in the slot assigned withslot No. 07, with the cross conductors 233 b located on the side wherethe lead wire is present each running astride slots with the slot pitchNp set to 7 and the cross conductors 233 b, located on the oppositeside, each running astride slots with the slot pitch Np set to 5, inmuch the same way as that with which the coil windings U11 and U12 areformed. This portion of the stator winding encircles the stator core bysubstantially a full turn and forms the coil winding U13 shown in FIG.7.

It is to be noted that, as FIG. 9 clearly indicates, the coil windingU13 is wound without an offset relative to the coil winding U12 alongthe circumferential direction. This means that there is no phasedifference between the coil winding U12 and the coil winding U13.Accordingly, FIG. 7 shows the coil windings U12 and U13 without anyphase difference manifesting between them.

Lastly, the stator winding, having left the layer-1 position in the slotassigned with slot No. 07, runs astride a range equivalent to six slotsand then leads into the slot assigned with slot No. 01 as a layer-2 slotconductor. Subsequently, the stator winding is wound around the statorcore 232 so as to encircle the stator core 232 by a full turn, from thelayer-2 position in the slot assigned with slot No. 01 through thelayer-1 position in the slot assigned with slot No. 08, with the crossconductors 233 b, located on the side where the lead wire is present,each running astride slots with the slot pitch Np set to 7 and the crossconductors 233 b, located on the opposite side, each running astrideslots with the slot pitch Np set to 5, in much the same way as that withwhich the coil windings U11, U12 and U13 are formed. This portion of thestator winding encircles the stator core by substantially a full turnand forms the coil winding U14 shown in FIG. 7.

It is to be noted that since the coil winding U14 is wound around thestator core with an offset relative to the coil winding U13 by aone-slot pitch, a phase difference in electrical angle equivalent to theone-slot pitch manifests. Accordingly, FIG. 7 clearly shows that thecoil winding U13 and the coil winding U14 are offset by 30°.

The coil windings in the stator winding group U2 shown in FIG. 10, too,are wound with a wave winding pattern with the cross conductors runningastride slots with the slot pitches set as in the stator winding groupU1. The coil winding U21 is wound around so as to encircle the statorcore from the layer-1 position in the slot assigned with slot No. 14through the layer-2 position in the slot assigned with slot No. 07,whereas the coil winding U22 is wound around so as to encircle thestator core from the layer-1 position in the slot assigned with slot No.13 through the layer-2 position in the slot assigned with slot No. 06.Subsequently, the stator winding, having left the layer-2 position inthe slot assigned with slot No. 06 leads into the slot assigned withslot No. 13 as a layer-3 slot conductor via the jumper wire and is woundaround as the coil winding U23 until it enters the slot assigned withslot No. 06 as a layer-4 slot conductor. Subsequently, the statorwinding is wound so as to encircle the stator core from the layer-3position in the slot assigned with slot No. 12 through the layer-4position in the slot assigned with slot No. 05, thereby forming the coilwinding U24.

As described above, the stator winding group U1 is made up with the coilwindings U11, U12, U13 and U14, and a voltage representing the sum ofthe voltages generated at the various phases assumed for the individualcoil windings combined together is induced at the stator winding groupU1. Likewise, the voltage representing the sum of the voltages generatedat the various phases assumed for the coil windings U21, U22, U23 andU24 combined together is induced at the stator winding group U2. Whilethe stator winding group U1 and the stator winding group U2 areconnected in parallel as shown in FIG. 7, there is no phase differencebetween the voltage induced at the stator winding group U1 and thevoltage induced at the stator winding group U2 and, for this reason,imbalanced conditions, which may manifest as, for instance, acirculating current, do not occur even though the stator winding groupsU1 and U2 are connected in parallel.

In addition, the cross conductors 233 b are each made to run astrideslots with the slot pitch Np set to (number of slots per pole +1) on onecoil end side and are each made to run astride slots with the slot pitchNp set to (number of slots per pole −1) on the other coil end side.Furthermore, the coil windings are wound by ensuring that there is nophase difference between the coil winding U12 and the coil winding U13and that there is no phase difference between the coil winding U22 andthe coil winding U23. Through these measures, a positional arrangementsuch as that shown in FIG. 11 is achieved for the slot conductors 233 a.

FIG. 11 shows the positional arrangement with which the slot conductors233 a are disposed at the stator core 232 in a view illustrating thepart of the stator core 232 ranging from the slot No. 71 through slotNo. 12 in FIG. 8 through FIG. 10. It is to be noted that the rotorrotates along the direction running from the left side of the figuretoward the right side of the figure. In the embodiment, twelve slots 237are formed in correspondence to two poles, i.e., over the 360° range inelectrical angle. This means that the range from slot No. 01 throughslot No. 12 in FIG. 11, for instance, corresponds to two poles. Thus,the number of slots per pole is six, whereas the number of slots perpole per phase NSPP is 2 (=6/3). Four slot conductors 233 a in thestator winding 238 are inserted at each slot 237.

Inside each rectangle representing a slot conductor 233 a, a specificcode among codes U11 through U24, V and W indicating the U-phase, theV-phase and the W-phase, and a filled circle mark “●” indicating thedirection running from the lead wire toward the neutral point or a crossmark “x” indicating the direction opposite to the direction indicated by“●” are shown. In addition, a slot conductor 233 a present on theinnermost circumferential side of a given slot 237 (toward the bottom ofthe slot) will be referred to as a layer-1 slot conductor, and thesubsequent slot conductors 233 a in the slot 237 will be referred to asa layer-2 slot conductor, which is set next to the innermost slotconductor 233 a, a layer-3 slot conductor and a layer-4 slot conductor,which is located on the outermost circumferential side (closest to theslot opening). In addition, reference numerals 01 through 12 are slotnumbers similar to those shown in FIG. 8 through FIG. 10. It is to benoted that the U-phase slot conductors 233 a alone are appended with thecodes U11 through U24 indicating the corresponding coil windings,whereas the V-phase slot conductors 233 a and the W-phase slotconductors 233 a are appended with the codes V and W, simply indicatingthe corresponding phases.

The eight slot conductors 233 a inside each dotted-line enclosure 234 inFIG. 11 are all U-phase slot conductors 233 a. For instance, the slotconductor group 234 inside the central enclosure includes slotconductors 233 a in the coil windings U24 and U23 assuming the layer-4positions in the slots assigned with slot Nos. 05 and 06 respectively,slot conductors 233 a in the coil windings U11 and U12 assuming thelayer-3 positions in the slots assigned with the slot Nos. 06 and 07respectively, slot conductors 233 a in the coil windings U22 and U21assuming layer-2 positions in the slots assigned with the slot Nos. 06and 07 respectively and slot conductors 233 a in the coil windings U13and U14 assuming the layer-1 positions in the slots assigned with theslot Nos. 07 and 08 respectively.

When the number of slots per pole is six, the number of slots per poleper phase is two and the number of slot conductors 233 inserted inlayers in each slot 237 is four, the U-phase slot conductors 233 a (andthe V-phase slot conductors 233 a and the W-phase slot conductors 233 a)are often disposed by adopting a positional arrangement such as thatshown in FIG. 12(a). In this positional arrangement, the slot conductorgroup on the right-hand side in the figure and the slot conductor groupon the left-hand side in the figure are set apart from each other with asix-slot pitch.

The positional arrangement shown in FIG. 12(b), which is adopted in theembodiment, is distinguishable from the standard arrangement in that thepair of slot conductors 233 a in layer 1 (L1) in each slot conductorgroup is offset by a one-slot pitch along the direction in which therotor rotates (toward the right side in the figure) and that the pair ofslot conductors 233 a in layer 4 (L4) in the slot conductor group isoffset by one-slot pitch along the direction opposite from the rotatingdirection (toward the left side in the figure). As a result, the crossconductor 233 b connecting the slot conductor 233 a in the coil windingU11 taking up the layer-4 position and the slot conductor 233 a in thecoil winding U11 taking up the layer-3 (L3) position runs astride slotswith a seven-slot pitch, whereas the cross conductor 233 b connectingthe slot conductor 233 a in the coil winding U24 taking up the layer-4position and the slot conductor 233 a in the coil winding U24 taking upthe layer-3 (L3) position runs astride slots with a 5-slot pitch. It isto be noted that the direction opposite from the direction along whichthe rotor rotates will be referred to as a reverse rotating direction inthe following description.

In this positional arrangement, the corresponding slot conductors 233 ain slot conductor groups corresponding to the V-phase and the W-phase,as well as the slot conductors 233 a corresponding to the U-phase, aredisposed with a one-slot pitch offset and, as a result, slot conductorgroups 234 achieving identical shapes are formed in correspondence tothe U-phase, the V-phase and the W-phase, as shown in FIG. 11. Namely,along the direction in which the rotor rotates, a slot conductor groupmade up with slot conductors 233 a corresponding to the U-phase and eachappended with the filled circle mark, a slot conductor group made upwith slot conductors 233 a corresponding to the W-phase and eachappended with the cross mark, a slot conductor group made up with slotconductors 233 a corresponding to the V-phase and each appended with thefilled circle mark, a slot conductor group made up with slot conductors233 a corresponding to the U-phase and each appended with the crossmark, a slot conductor group made up with slot conductors 233 acorresponding to the W-phase and each appended with the filled circlemark, and a slot conductor group made up with slot conductors 233 acorresponding to the V-phase and each appended with the cross mark areformed in this order.

As shown in FIG. 11, the positional arrangement achieved in theembodiment is characterized in that:

(a) the cross conductors 233 b connect slot conductors 233 a by eachrunning astride slots with the slot pitch Np set to N+1 (=7) on one coilend side and each running astride slots with the slot pitch Np set toN−1 (=5) on the other coil end side with N (=6) representing the numberof slots per pole;

(b) the stator winding includes slot conductor groups 234 each made upwith a set of slot conductors 223 a corresponding to a single phase,which are inserted through a predetermined number Ns (=4) of successiveslots forming a continuous range along the circumference of the statorcore so as to take up successive slot positions and layer positions; and

(c) the predetermined number of slots Ns is set so that Ns=NSPP+NL=4with NSPP (=2) representing the number of slots per pole per phase, whenthe number of layers is 2×NL (NL=2).

It is to be noted that when slot conductors 223 b are set to take upsuccessive slot positions and successive layer positions, the slotconductors taking up matching layer positions are inserted at successiveslots 237 and the slot conductors inserted through a single slot 237take up successive layer positions, as shown in FIG. 11. In thedescription of the embodiment, a set of slot conductors 233 a disposedby adopting this positional arrangement will be referred to as a slotconductor group 234.

FIG. 13(a) is a partial enlargement of the sectional view presented inFIG. 5(a). At the cores 301 constituting part of the rotor core 252,grooves, which form magnetic gaps 258 at the surface of the rotor 250,are present in addition to the gaps 257 formed on the two sides of eachpermanent magnet 254. The gaps 257 are formed for purposes of coggingtorque reduction, whereas the magnetic gaps 258 are formed in order toreduce the extent of torque pulsation occurring during applying current.In the following description, the central axis running between a givenpermanent magnet 254 a and the permanent magnet directly to the left ofthe permanent magnet 254 a, viewed from the inner circumferential sideof the rotor 250, will be referred to as a q-axis a and the central axisrunning between a permanent magnet 254 b and the magnet directly to theleft of the permanent magnets 254 b, viewed from the innercircumferential side of the rotor 250, will be referred to as a q-axisb. A magnetic gap 258 a occupies a position offset to the right relativeto the q-axis a, whereas a magnetic gap 258 b occupies a position offsetto the left relative to the q-axis b. In addition, the magnetic gap 258a and the magnetic gap 258 b are set so as to achieve symmetry relativeto a d-axis, i.e., the central axis of the magnetic pole.

FIG. 13(b) is a partial enlargement of the sectional view presented inFIG. 5(b). At the core 302, constituting part of the rotor core 252,magnetic gaps 258 c and 258 d, instead of the magnetic gaps 258 a and258 b, are formed. Viewed from the inner circumferential side of therotor 250, the magnetic gap 258 c occupies a position offset to the leftrelative to the q-axis a, and the magnetic gap 258 d occupies a positionoffset to the right relative to the q-axis b. As FIG. 5 clearlyindicates, the sections of the cores 301 and the core 302 are identicalin appearance except for the different positions of the magnetic gaps258 a and 258 b and the magnetic gaps 258 c and 258 d.

The positions of the magnetic gap 258 d and the magnetic gap 258 c areoffset by 180° in electrical angle relative to the positions of themagnetic gap 258 a and the magnetic gap 258 b respectively. In otherwords, the core 302 can be formed by rotating a core 301 by an extentequivalent to a single magnetic pole pitch. Since this means that thecores 301 and the core 302 can be manufactured by using a single die,the manufacturing cost can be lowered. In addition, the holes 253 at thecores 301 and 302 occupy matching positions without any offset along thecircumferential direction. As a result, the permanent magnets 254installed in the individual holes 253 are each a single-piece permanentmagnet passing through the cores 301 and 302, not a magnet constitutedwith separate parts split along the axial direction. However, it will beobvious that a permanent magnet 254, constituted with a plurality ofsplit segments, may be installed by stacking the segments one on top ofanother along the axis of a hole 253.

A rotating magnetic field induced by the three-phase AC currents at thestator 230 acts on the permanent magnets 254 a and 254 b at the rotor250, thereby generating a magnetic torque. In addition to the magnetictorque, a reluctance torque is in action at the rotor 250.

FIG. 14 illustrates the reluctance torque. The axis of a magnetic fluxpassing through the center of a magnet is normally referred to as ad-axis, whereas the axis of a magnetic flux passing from one side of theposition between poles, toward the other side of the position betweenpoles, is normally referred to as a q-axis. The area of the core locatedover the middle point between the poles formed at magnets will bereferred to as an auxiliary salient pole portion 259. Since the magneticpermeability of the permanent magnets 254 installed in the rotor 250 issubstantially equal to that of air, the area along the d-axis ismagnetically recessed and the area along the q-axis magneticallyprojects, viewed from the side where the stator is located. For thisreason, the core area over the q-axis is referred to as a salient pole.The reluctance torque occurs due to the difference between the ease withwhich the magnetic flux passes along the d-axis and the ease with whichthe magnetic flux passes along the q-axis, i.e., due to the salient poleratio.

As the description above indicates, a rotating electric machine adoptingthe present invention is a type of rotating electric machine that usesboth the magnetic torque and the auxiliary salient pole reluctancetorque. Torque pulsation occurs due to both the magnetic torque and thereluctance torque. The torque pulsation includes a pulsation componentmanifesting during not applying current and a pulsation componentmanifesting during applying current. Of those, the pulsation componentmanifesting during not applying current is normally referred to ascogging torque. When the rotating electric machine is actually used inoperation under load, torque pulsation occurs as a combination of thecogging torque and the pulsation component manifesting during applyingcurrent.

Most methods proposed in the related art for reducing torque pulsationoccurring in rotating electric machines only refer to reduction of thecogging torque, and the issue of torque pulsation occurring applyingcurrent is often not addressed in those methods. However, noise in arotating electric machine more often occurs under load rather than in ano-load state. In other words, it is critical to reduce torque pulsationoccurring under load in order to effectively reduce noise in a rotatingelectric machine and full noise reduction cannot be achieved simply byreducing the cogging torque alone.

The torque pulsation reducing method achieved in the embodiment will bedescribed next.

First, the no-load characteristics to manifest in the non-applyingcurrent state will be described. FIG. 15(a) presents the resultsobtained by simulating the distribution of magnetic fluxes occurringwhen no electric current is supplied to the stator winding 238, i.e.,the distribution of magnetic fluxes attributable to the permanentmagnets 254, in an illustration of two poles, one represented by an area401 formed with a permanent magnet 254 a and the other represented by anarea 402 formed with a permanent magnet 254 b. Namely, the figurepresents the results of a simulation of a rotating electric machine thatincludes the area 401 and the area 402 formed with an alternatingpattern along the circumferential direction in a view taken of the A-Asection. Since the rotating electric machine achieved in the embodimenthas twelve poles, six poles of area 401 and six poles of area 402 areset in an alternating pattern along the circumferential direction. Anexamination of the individual poles reveals that the magnetic gaps 258 aand 258 b are present at the auxiliary salient pole portions 259 in thearea 401, whereas no magnetic gaps 258 are present at the auxiliarysalient portions 259 in the area 402.

In the non-applying current state, the magnetic fluxes at each permanentmagnet 254 short the magnet end areas. For this reason, no magnetic fluxpasses along the q-axis at all. In addition, hardly any magnetic fluxpasses through areas corresponding to the magnetic gaps 258 a and 258 bformed at positions slightly offset relative to the gaps 257 present atthe magnet ends. Magnetic fluxes that pass through the stator core 232reach the teeth 236 by way of the core areas located on the stator sideof the permanent magnets 254. Thus, the presence of the magnetic gaps258 a and 258 b hardly affects the magnetic fluxes in the non-applyingcurrent state, which is pertinent to the cogging torque. In other words,the characteristics such as the cogging torque, induced voltage and thelike in the no-load state are shown to be unaffected by the magneticgaps 258 a and 258 b.

FIG. 15(b) presents the results of simulation corresponding to an area401 alone, whereas FIG. 15(c) presents the results of simulationcorresponding to an area 402 alone. The area 401 in FIG. 15(b) is partof a rotary electric machine with twelve poles, having areas 401 only,set along the circumferential direction so that the direction ofmagnetization at a given permanent magnet 254 forming a specific pole isreversed at the next permanent magnet 254 forming another pole. The area402 in FIG. 15(c) is included in a rotary electric machine with twelvepoles, having areas 402 only, set along the circumferential direction sothat the direction of magnetization at a given permanent magnet 254forming a specific pole is reversed at the next permanent magnet 254forming another pole. The magnetic flux distributions in FIG. 15(b) andFIG. 15(c) are both similar to that shown in FIG. 15(a), with nomagnetic flux passing along the q-axis.

FIG. 16 and FIG. 17 present diagrams in reference to which a coggingtorque reducing method will be described. FIG. 16 shows part of therotor 250 and the stator core 232 in a sectional view. In FIG. 16, τpand τm respectively represent the pole pitch between the poles formedvia the permanent magnets 254 and the width angle of the permanentmagnets 254. In addition, τg represents the sum of the width angleaccounted for by a permanent magnet 254 and the gaps 257 present on thetwo sides thereof, i.e., the width angle of the holes 253 shown in FIG.4. The cogging torque can be reduced by adjusting the ratios of theseangles τm/τp and τg/τp. In the description of the embodiment, the ratioτm/τp will be referred to as a degree of the magnet pole arc and theratio τg/τp will be referred to as a degree of magnet hole pole arc.

FIG. 17 is a diagram indicating the relationship between the ratio τm/τprepresenting the degree of magnet pole arc and the cogging torque. It isto be noted that the results presented in FIG. 17 are obtained byassuming that τm=τg and that the permanent magnet 254 and the gaps 257thereat form a fan shape concentric with the circle defined by the outercircumference of the rotor 250. While the optimal values are bound to beslightly different when rectangular magnets are used, as in theembodiment, it will be obvious that the principle presented in FIG. 17is applicable to the present invention as well. In FIG. 17, theamplitude of the cogging torque is indicated along the vertical axis andthe rotational angle of the rotor 250 is indicated in electrical anglealong the horizontal axis. The amplitude of pulsation changes dependingupon the value representing the ratio τm/τp, and the cogging torque canbe reduced by selecting a value of approximately 0.75 for τm/τp whenτm=τg. In addition, the tendency whereby the cogging torque is notaffected by the magnetic gaps 258 described in reference to FIG. 13(a),remains in place regardless of which of the values indicated in FIG. 17is taken for the ratio τm/τp of the magnet width angle to the polepitch. Namely, no matter what positions are assumed by the magnetic gaps258, the relationship shown in FIG. 17 remains the same.

FIG. 18 shows waveforms of the cogging torque. The rotational angle ofthe rotor is indicated in electrical angle along the horizontal axis. Aline L11 is the waveform of the cogging torque manifesting in the rotorin the rotating electric machine corresponding to FIG. 15(a) with thearea 401 having the magnetic gaps 258 formed thereat and the area 402with no magnetic gaps 258 set in an alternating pattern, a line L12 isthe waveform of the cogging torque manifesting in the rotor in therotating electric machine corresponding to FIG. 15(b), which includesonly the areas 401 each having the magnetic gaps 258 formed thereat, anda line L13 is the waveform of the cogging torque manifesting in therotor in the rotating electric machine corresponding to FIG. 15(c),which includes only areas 402 with no magnetic gaps 258 formed thereat.FIG. 16(a) demonstrate that the presence/absence of the magnetic gaps258 has little effect on the cogging torque.

FIG. 19 is a diagram indicating the waveforms of the induced voltages. Acurve L21 represents the waveform of the induced voltage in the rotatingelectric machine achieved in the embodiment by adopting the slotconductor positional arrangement shown in FIG. 11, whereas a curve L22represents the waveform of the induced voltage in a comparison exampleadopting the stator structure disclosed in patent literature 1. Inaddition, FIG. 20 presents the results obtained by conducting higherharmonic analysis on the induced voltage waveforms shown in FIG. 19.

FIG. 19 indicates that the induced voltage waveform represented by thecurve L21 more closely resembles the sine wave than the induced voltagewaveform represented by the curve L22. In addition, the higher harmonicanalysis results presented in FIG. 20 indicate that the 5th-order higherharmonic component and the 7th-order higher harmonic component can bereduced by significant extents through the embodiment.

The results presented in FIG. 15 through FIG. 20 indicate that while themagnetic gaps 258, embodying a characteristic feature of the rotorstructure according to the present invention, do not affect the coggingtorque and the induced voltage, the cogging torque can be reduced byadjusting the ratio representing the degree of magnet pole arc τm/τp,through a method known in the related art and the higher harmoniccomponent in the induced voltage can be reduced by adopting the statorstructure according to the present invention. In other words, thecogging torque and the induced voltage can be individually reducedindependently of each other.

Next, the load characteristics in the applying current state will bedescribed.

The rotating electric machine achieved in the embodiment is a motor withsix slots allocated to each pole. In this rotating electric machine, theslot conductors 233 constituting the stator winding 238 are disposed inthe slots 237 of the stator core 232 as illustrated in FIG. 11. Thisarrangement makes it possible to reduce the 5th-order higher harmoniccomponent and the 7th-order higher harmonic component in the inducedvoltage, as indicated in FIG. 20, and as a result, the 6th-order torquepulsation, unique to three-phase motors and attributable to these higherharmonic components, can be reduced.

FIG. 21 shows waveforms of the torque to manifest in the applyingcurrent state. The rotational angle of the rotor is indicated in theelectrical angle along the horizontal axis. A line L31 is the waveformof the torque manifesting in the rotor of the rotating electric machinecorresponding to FIG. 15(a), which includes the area 401 with themagnetic gaps 258 formed thereat and the area 402 without magnetic gaps258 set in the alternating pattern, a line L32 is the waveform of thetorque manifesting in the rotating electric machine corresponding toFIG. 15(b) which only includes areas 401 each having the magnetic gaps258 formed thereat, and a line L33 is the waveform of the torquemanifesting in the rotating electric machine corresponding to FIG.15(c), which only includes areas 402 with no magnetic gaps 258 formedthereat.

FIG. 21 indicates that the dominant torque pulsation component in therotating electric machine achieved in the embodiment is the 12th-ordertorque pulsation component, i.e., the component with 30° cycles inelectrical angle with hardly any 6th-order component present in thetorque. In addition, the figure indicates that the torque pulsationwaveforms L 31 and L 32 both change relative to the torque pulsationwaveform L 33 corresponding to the rotating electric machine that doesnot include any magnetic gaps 258 formed therein, i.e., the rotatingelectric machine with areas 402 alone. This means that the magneticfluxes in the applying current state are affected by the magnetic gaps258. In addition, the phase of the torque pulsation L 32 manifesting inthe rotating electric machine having the areas 401 alone and the phaseof the torque pulsation L33 manifesting in the rotating electric machinehaving the areas 402 alone are substantially the reverse of each other.As shown in FIG. 15(a), the rotating electric machine achieved in theembodiment assumes a structure having the area 401 and the area 402 setin the alternating pattern, and the total torque pulsation to which theentire rotor is subjected is the average of the torque pulsation L 32and the torque pulsation L 33, as indicated by the torque pulsationwaveform L 31.

In the embodiment described above, the torque pulsation in the applyingcurrent state can be reduced due to the presence of the magnetic gaps258 a and 258 b formed as described earlier. In order to assure suchtorque pulsation reducing effect, it is desirable that the width angle(the angle measured along the circumferential direction) of the groovesforming the magnetic gaps 258 be set within a range of ¼˜½ of the pitchangle of the teeth 236. It is to be noted that a similar effect can beachieved with magnetic gaps set so as to achieve symmetry relative tothe q-axis passing through the center of the magnetic pole and toachieve asymmetrical positions relative to the d-axis passing throughthe centers of the salient poles. In addition, more than two differenttypes of magnetic gaps 258 may be formed at the auxiliary salient poleportions 259. In such a case, the torque pulsation can be reduced with agreater degree of freedom and pulsation reduction can be achievedthrough finer adjustment.

Moreover, the present invention is characterized in that the torque doesnot decrease as much as in a rotating electric machine without anymagnetic gaps. In the skew structure, designed to reduce torquepulsation in the related art, the torque is bound to decrease because ofthe skew, and thus, the skew structure does not facilitateminiaturization. The embodiment, in contrast, achieves an addedadvantage in that the torque is not lowered, as well as assuring areduction of torque pulsation in the applying current stateindependently of a reduction of the cogging torque. This advantage isattributed to the dominance of the 12th-order component in the torquepulsation occurring in a rotor without any grooves and the positionalarrangement assumed for the slot conductors 233 shown in FIG. 11 is alsoa contributing factor.

FIG. 22 presents the results of higher harmonic analysis conducted forthe waveforms of the torque manifesting in the applying current state. Aline L41 represents the waveform of the torque manifesting in a rotatingelectric machine with the slot conductors 233 disposed as shown in FIG.12(a) and the rotor thereof having no magnetic gaps 258 formed thereat,as shown in FIG. 15(c). A line L42 represents the waveform of the torquemanifesting in a rotating electric machine with the slot conductors 233disposed by adopting the embodiment shown in FIG. 12(b) with the rotorthereof having no magnetic gaps 258 formed thereat, as shown in FIG.15(c). A line L43 represents the waveform of the torque manifesting in arotating electric machine with the slot conductors 233 disposed byadopting the embodiment shown in FIG. 12(b) and the rotor thereofadopting the structure of the embodiment, as shown in FIG. 15(a).

The line L42 in the higher harmonic analysis results presented in FIG.22 clearly shows a decrease in the 6th-order component, i.e. thecomponent with the 60° cycles in electrical angle, over the 6th-ordercomponent represented by the line L41. This decrease is attributable tothe positional arrangement shown in FIG. 12(b) illustrating theembodiment, adopted for the slot conductors 233. In addition, the lineL43 shows a distinct decrease in the 12th-order component, i.e., thecomponent with the 30° cycles in electrical angle, over the 12th-ordercomponent represented by the line L42. This decrease is attributable tothe structure shown in FIG. 15(a) illustrating the embodiment, adoptedfor the rotor. Namely, torque ripple components with different higherharmonic orders can be reduced independently of each other.

While the torque ripple can be reduced by adopting the embodiment, anelectromagnetic exciting force, which causes toroidal vibration of thestator core 232, may occur as torque is generated in the rotatingelectric machine and this toroidal vibration may cause noise.

FIG. 23 shows the vibration mode for the toroidal 0th-order component atthe stator core 232. It is to be noted that the initial shape of thestator core 232 is indicated by the thin line. This vibration modecauses noise as it resonates with the electromagnetic exciting forcecontaining the matching toroidal 0th-order component. However, the levelof the toroidal 0th-order electromagnetic exciting force corresponds tothe level of the torque ripple and thus, the toroidal 0th-orderelectromagnetic exciting force can be reduced by reducing the torqueripple. Namely, the toroidal 0th-order electromagnetic exciting forceoccurring at the stator core 232 of the embodiment can be reduced inmuch the same way as the torque ripple.

FIG. 24 shows the vibration mode for the toroidal 6th-order component atthe stator core 232. It is to be noted that the initial shape of thestator core 232 is indicated by the thin line. This vibration modecauses noise as it resonates with the electromagnetic exciting forcecontaining the matching toroidal 6th-order component. In the embodiment,the magnetic gaps 258 are formed in correspondence to each pole, asillustrated in FIG. 13(a). As a result, a magnetic imbalance is createdamong the poles and an exciting force assuming a toroidal order that is½ of the number of poles is generated at each of the cores 301 and 302shown in FIG. 13. However, since the magnetic gaps 258 at the cores 301and the magnetic gaps 258 at the core 302 are set at positions offsetrelative to each other by one magnetic pitch, the electromagneticexciting forces, canceled out along the axial direction, do not resonatewith the toroidal 6th-order vibration mode.

FIG. 25 shows a vibration mode containing the toroidal 6th-ordercomponent at the stator core 232, in which the phase at one end of thestator is the reverse of the phase at the other end of the stator facingopposite the one end along the axial direction. It is to be noted thatthe initial shape of the stator core 232 is indicated by the thin line.The phases of the electromagnetic exciting forces generated at the cores301 and at the core 302 are the reverse of each other, as has beendescribed earlier, and, for this reason, resonance will occur if therotor core adopts a two-stage structure achieved with one type of core301 and another type of core 302. However, in conjunction with the rotorcore adopting a three-stage structure, as in the embodiment, theelectromagnetic exciting forces do not resonate with this vibrationmode. In addition, it will be obvious that two or more types of coresmay be used to configure a rotor core with more than three stages toachieve advantages similar to those of the embodiment.

Second Embodiment

FIG. 26 and FIG. 27 illustrate the second embodiment of the presentinvention achieved by adopting the present invention in a stator withthe number of slots per pole per phase NSPP set to 2 and slot conductors233 a inserted in each slot 237 in two layers. The rotor assumes astructure similar to that described in reference to the firstembodiment. FIG. 26 is a detailed connection diagram pertaining to theU-phase winding constituting part of the stator winding, with FIG. 26(a)showing the U1-phase winding group and FIG. 26(b) showing the U2-phasewinding group. FIG. 27 shows the positional arrangement with which theslot conductors 233 a are disposed at the stator core 232.

As shown in FIG. 26(b), the coil winding U11 in the U1-phase windinggroup, starting at the lead wire, enters the slot assigned with slot No.72 as a layer-2 slot conductor, and then extends astride a rangeequivalent to five slots as a cross conductor 233 b before moving intothe slot assigned with slot No. 67 as a layer-1 slot conductor. Then,the coil winding leaves the layer-1 position in the slot assigned withslot No. 67, runs astride a range equivalent to seven slots and leadsinto the slot assigned with slot No. 60 as a layer-2 slot conductor.Subsequently, the coil winding is continuously wound in a wave windingpattern with the cross conductors running astride the five slot rangeand the seven slot range alternately until it is inserted through theslot assigned with slot No. 07 as a layer-1 slot conductor afterencircling the stator core 232 by substantially a full turn. The windingranging from the lead wire through the layer-1 position in the slotassigned with slot No. 07 forms the coil winding U11.

The winding, having left the layer-1 position in the slot assigned withslot No. 07 runs astride a range equivalent to six slots and then leadsinto the slot assigned with slot No. 01 as a layer-2 slot conductor. Thecoil winding U12, which starts at the layer-2 position in the slotassigned with slot No. 01, is continuously wound with the wave windingpattern with the cross conductors running astride the five slot rangeand the seven slot range alternately, as in the coil winding U11, untilit leads into the slot assigned with slot No. 08 as a layer-1 slotconductor after encircling the stator core 232 by substantially a fullturn.

The coil windings in the U2-phase winding group, too, are wound with awave winding pattern as are the coil windings in the U1-phase windinggroup. The coil winding U21 is wound with a wave winding pattern rangingfrom the layer-1 position in the slot assigned with slot No. 14 throughthe layer-2 position in the slot assigned with slot No. 07, whereas thecoil winding U22 is wound to range from the layer-1 position in the slotassigned with slot No. 13 through the layer-2 position in the slotassigned with slot No. 06.

FIG. 27 shows the positional arrangement with which the slot conductors233 a are disposed at the slots assigned with slot Nos. 01 through 12and slot Nos. 71 and 72. In this figure, the 12-slot pitch covering theslot assigned with slot No. 01 through the slot assigned with slot No.12 corresponds to two poles. The positional arrangement with which theslot conductors 233 a corresponding to the U-phase, the V-phase and theW-phase are disposed as shown in FIG. 27 is identical to the positionalarrangement with which the slot conductors 233 a are disposed to take uplayer-1 and layer-2 positions in FIG. 11. In the embodiment, the set offour slot conductors 233 a inside each dotted line enclosure forms asingle slot conductor group 234.

The slot conductor groups 234 formed in the embodiment, too, satisfyconditions similar to those having been described in reference to theslot conductor groups 234 (see FIG. 11) in the first embodiment. Namely:

(a) the cross conductors 233 b connect slot conductors 233 a by eachrunning astride slots with the slot pitch Np set to N+1 (=7) on one coilend side and each running astride slots with the slot pitch Np set toN−1 (=5) on the other coil end side, with N (=6) representing the numberof slots per pole;

(b) the stator winding includes slot conductor groups 234 each made upwith a set of slot conductors 223 b corresponding to a single phase,which are inserted through a predetermined number Ns (=3) of consecutiveslots forming a continuous range along the circumference of the statorcore so as to take up successive slot positions and layer positions; and

(c) the predetermined number of slots Ns is set so that Ns=NSPP+NL=3with NSPP (=2) representing the number of slots per pole per phase, whenthe number of layers is 2×NL (NL=1).

Consequently, the extent of torque ripple can be reduced and thus noisein the rotating electric machine is reduced, thereby ultimatelyachieving the object set fourth earlier, of noise reduction in therotating electric machine, as in the first embodiment.

Third Embodiment

FIG. 28 and FIG. 29 illustrate the third embodiment of the presentinvention achieved by adopting the present invention in a stator withthe number of slots per pole per phase NSPP set to 3 and slot conductors233 a inserted in each slot 237 in four layers. The rotor assumes astructure similar to that described in reference to the firstembodiment. FIG. 28 is a detailed connection diagram pertaining to partof the U-phase winding, with FIG. 28(a) showing the U1-phase windinggroup and FIG. 28(b) showing the U2-phase winding group. FIG. 19 showsthe positional arrangement with which the slot conductors 233 a aredisposed at the stator core 232.

As shown in FIG. 28, 108 slots are formed at the stator core 232 whenthe number of slots per pole per phase NSPP is 3 and slot conductors 233a are inserted through in each slot 237 in four layers (2×NL). At such astator, the U1-phase winding group and the U2-phase winding group areeach made up with six coil windings. In addition, the cross conductorsin the coil windings run astride slots with a 5-slot pitch and aseven-slot pitch alternately.

In the U1-phase winding group shown in FIG. 28(a), the winding extendingfrom the layer-4 position in the slot assigned with slot No. 105 throughthe layer-3 position in the slot assigned with slot No. 07 constitutes acoil winding U11, the winding extending from the layer-4 position in theslot assigned with slot No. 106 through the layer-3 position in the slotassigned with slot No. 08 constitutes a winding U12 and the windingextending from the layer-4 position in the slot assigned with slot No.107 through the layer-3 position in the slot assigned with slot No. 09constitutes a coil winding U13. The winding, having left the layer-3position in the slot assigned with slot No. 09, leads into the slotassigned with slot No. 106 as a layer-2 slot conductor via a jumperwire. The winding extending from the layer-2 position in the slotassigned with slot No. 106 through the layer-1 position in the slotassigned with slot No. 08 constitutes a coil winding U14, the windingextending from the layer-2 position in the slot assigned with slot No.107 through the layer-1 position in the slot assigned with slot No. 09constitutes a coil winding U15, and the winding extending from thelayer-2 position in the slot assigned with slot No. 108 through thelayer-1 position in the slot assigned with slot No. 10 constitutes acoil winding U16.

In the U2-phase winding group shown in FIG. 28(b), the winding extendingfrom the layer-1 position in the slot assigned with slot No. 19 throughthe layer-2 position in the slot assigned with slot No. 09 constitutes acoil winding U21, the winding extending from the layer-1 position in theslot assigned with slot No. 18 through the layer-2 position in the slotassigned with slot No. 08 constitutes a coil winding U22 and the windingextending from the layer-1 position in the slot assigned with slot No.17 through the layer-2 position in the slot assigned with slot No. 07constitutes a coil winding U13. The winding, having left the layer-2position in the slot assigned with slot No. 07 leads into the slotassigned with slot No. 18 as a layer-3 slot conductor via a jumper wire.The winding extending from the layer-3 position in the slot assignedwith slot No. 18 through the layer-4 position in the slot assigned withslot No. 08 constitutes a coil winding U24, the winding extending fromthe layer-3 position in the slot assigned with slot No. 17 through thelayer-4 position in the slot assigned with slot No. 07 constitutes acoil winding U25, and the winding extending from the layer-3 position inthe slot assigned with slot No. 18 through the layer-4 position in theslot assigned with slot No. 06 constitutes a coil winding U26.

FIG. 29 shows the positional arrangement with which the slot conductors233 a are inserted at the slots assigned with slot Nos. 01 through 18.In the embodiment, the 18-slot pitch ranging from slot No. 01 throughslot No. 18 corresponds to two poles. As FIG. 28 indicates, the coilwindings U14 through U16 and the coil windings U21 through U23 are eachinserted at slots 237 alternately as a layer-1 slot conductor and as alayer-2 slot conductor, whereas the coil windings U11 through U13 andthe coil windings U24 through U26 are each inserted at slots 237alternately as a layer-3 slot conductor and as a layer-4 slot conductor.A slot conductor group 1234 is formed with a set of twelve slotconductors 233 a inside a dotted line enclosure in FIG. 29. The twelveslot conductors 233 a are all part of the twelve coil windings U11through U16 and U21 through U26 corresponding to the same phase.

As do the twelve slot conductors 233 a corresponding to the U-phase,twelve slot conductors 233 a corresponding to either of the otherphases, i.e., the V-phase or the W-phase, together form a slot conductorgroup. As in the first embodiment, a slot conductor group made up withslot conductors 233 a corresponding to the U-phase and each appendedwith the filled circle mark, a slot conductor group made up with slotconductors 233 a corresponding to the W-phase and each appended with thecross mark, a slot conductor group made up with slot conductors 233 acorresponding to the V-phase and each appended with the filled circlemark, a slot conductor group made up with slot conductors 233 acorresponding to the U-phase and each appended with the cross mark, aslot conductor group made up with slot conductors 233 a corresponding tothe W-phase and each appended with the filled circle mark, and a slotconductor group made up with slot conductors 233 a corresponding to theV-phase and each appended with the cross mark are formed in this orderalong the direction in which the rotor rotates.

As FIG. 29 clearly indicates, the slot conductor groups 1234 formed inthe embodiment, too, satisfy conditions similar to those having beendescribed in reference to the slot conductor groups 234 (see FIG. 11) inthe first embodiment. Namely:

(a) the cross conductors 233 b connect slot conductors 233 a by eachrunning astride slots with the slot pitch Np set to N+1 (=10) on onecoil end side and each running astride slots with the slot pitch Np setto N−1 (=8) on the other coil end side, with N (=9) representing thenumber of slots per pole;

(b) the stator winding includes slot conductor groups 234 each made upwith a set of slot conductors 223 b corresponding to a single phase,which are inserted through a predetermined number Ns (=5) of consecutiveslots forming a continuous range along the circumference of the statorcore so as to take up successive slot positions and layer positions; and

(c) the predetermined number of slots Ns is set so that Ns=NSPP+NL=5with NSPP (=3) representing the number of slots per pole per phase whenthe number of layers is 2×NL (NL=2).

Consequently, the extent of torque ripple can be reduced and thus noisein the rotating electric machine is reduced, thereby ultimatelyachieving the object of noise reduction in the rotating electricmachine, as in the first and second embodiments.

As the number of slots per pole per phase NSPP increases, the orders ofhigh harmonic component that can be eliminated by disposing slotconductors with a one-slot pitch offset as shown in FIG. 12 change. Forinstance, when NSPP=2, the one-slot pitch is equivalent to 30° inelectrical angle. As 30° equals a half cycle of the 6th-order component,the 5th-order induced voltage component and the 7th-order inducedvoltage component, i.e., the components in orders close to the 6th-ordercan be diminished, as indicated in FIG. 20. As NSPP is set to an evengreater value, as in this embodiment, the one-slot pitch becomesshorter, making it possible to reduce the higher harmonic component ofeven higher orders. In addition, by reducing the width of the magneticgaps 258 formed at the rotor core 252, torque ripple higher harmoniccomponents of even higher orders can be reduced and as a result, an evenquieter rotating electric machine can be provided.

In addition, the present invention may be adopted to achieve lower noisein a vehicle that utilizes the rotating electric machine describedabove, a battery that provides DC power and a conversion device thatconverts the DC power from the battery to AC power and provides the ACpower to the rotating electric machine, characterized in that torquegenerated in the rotating electric machine is used as a drive force,such as the vehicle described in reference to FIGS. 1 and 2.

While the invention has been described in reference to an example inwhich it is adopted in a 12-pole magnet motor, the present invention isnot limited to this example and it may be adopted in a motor with anyother number of poles. Furthermore, the present invention may be adoptedin motors used in various applications other than vehicularapplications. Moreover, the present invention may be adopted in variousother types of rotating electric machines, such as generators, insteadof motors. As long as the features characterizing the present inventionare not compromised, the present invention is by no means limited in anyway whatsoever to the particulars of the embodiments described above.

The disclosure of the following priority application is hereinincorporated by reference:

-   Japanese Patent Application No. 2012-8565 filed Jan. 19, 2012.

The invention claimed is:
 1. A rotating electric machine, comprising: astator core having a plurality of slots formed therein; a stator windingassuming a plurality of phases, which includes a plurality of coilwindings wound with a wave winding pattern, each coil winding made upwith slot conductors each inserted at one of the slots at the statorcore to form one of a plurality of layers and cross conductors eachconnecting same-side ends of slot conductors inserted at different slotsso as to form a coil end; and a rotor rotatably disposed via an air gapso as to be allowed to rotate relative to the stator core, whichincludes a plurality of magnets and a plurality of magnetic auxiliarysalient pole portions each formed between poles formed with the magnets,wherein: the cross conductors connect the slot conductors so as to runastride slots with a slot pitch Np set to N+1 at coil ends on one sideand run astride slots with the slot pitch Np set to N−1 at coil ends onanother side, with N representing a number of slots per pole; the statorwinding are arranged into stator winding groups, and each stator windinggroup comprises a plurality of circumferential windings of the samephase so that there is no phase difference between groups correspondingto a single phase; the stator winding includes a plurality of slotconductor groups each made up with a plurality of slot conductorscorresponding to a single phase; the plurality of slot conductors ineach slot conductor group are inserted at a predetermined number Ns ofsuccessive slots forming a continuous range along a circumference of thestator core so that the slot conductors in the slot conductor group takesuccessive slot positions and successive layer positions; and thepredetermined number Ns is set so that Ns=NSPP+NL when NSPP represents anumber of slots per pole per phase, NL represents a number of layers,and the number of layers is expressed as 2×NL; the rotor includesmagnetic resistance-altering portions located at positions each offsetalong a circumferential direction from a q-axis passing through a centerof a corresponding magnetic auxiliary salient portion; and the magneticresistance-altering portion is provided on every other magnetic poleformed with the magnet, and a magnetic pole provided with the magneticresistance-altering portion and a magnetic pole without the magneticresistance-altering portion are alternately arranged.
 2. A rotatingelectric machine according to claim 1, wherein: the magneticresistance-altering portions are magnetic gaps.
 3. The rotating electricmachine according to claim 2, wherein: the rotor core is formed bylaminating magnetic steel sheets, each having holes or notches, whichare to constitute the magnetic gaps, formed therein.
 4. The rotatingelectric machine according to claim 3, wherein: the rotor core isdivided into a plurality of axially-split core groups each having themagnets, the magnetic auxiliary salient pole portions and the magneticgaps, the magnets and the magnetic gaps are disposed with a uniformpositional arrangement at the axially-split core groups so that themagnets and the magnetic gaps occupy matching positions along thecircumferential direction at the axially-split core groups, and thereare at least three axially-split core groups that include at least twodifferent types of axially-split core groups assembled so that themagnetic gaps thereof occupy positions offset relative to each otheralong the circumferential direction.
 5. The rotating electric machineaccording to claim 1, wherein: the magnetic gaps are set asymmetricallyrelative to the q-axis passing through a salient pole and symmetricallyrelative to a d-axis passing through a center of a magnetic pole.
 6. Therotating electric machine according to claim 5, wherein: the magneticgaps are formed by recessed portions formed at a surface of the rotorcore.
 7. The rotating electric machine according to claim 1, wherein:the magnetic gaps are set symmetrically relative to the q-axis passingthrough a magnetic pole and asymmetrically relative to a d-axis passingthrough a center of a salient pole.
 8. The rotating electric machineaccording to claim 1, wherein: the slot conductors are constituted withflat wire.
 9. The rotating electric machine according to claim 1,wherein: the stator winding includes a plurality of Y connections andthere is no phase difference manifesting between voltages induced atsame-phase windings in the plurality of Y connections.
 10. The rotatingelectric machine according to claim 1, wherein: the stator windingadopts a structure that reduces a sixth-order torque ripple componentover 360° in electrical angle and a 12th-order torque ripple componentis reduced via the magnetic resistance-altering portions.
 11. A vehicle,comprising: a rotating electric machine according to claim 1; a batterythat provides DC power; and a conversion device that converts the DCpower originating from the battery to AC power and provides the AC powerto the rotating electric machine, wherein: torque generated in therotating electric machine is used as a drive force to drive the vehicle.